Postpartum amenorrhoea and breast-feeding in a Danish sample.

The duration of postpartum amenorrhoea was studied in a Danish sample of 361 women. The median duration of amenorrhoea was 17 weeks. The 25th and 75th percentiles were 10 and 30 weeks, respectively. A significant correlation was found between the duration of postpartum amenorrhoea and of breast-feeding. However, lactation for more than 9 months did not extend the duration of amenorrhoea. Menstruation before weaning occurred in 57% of the women, and 43% terminated breast-feeding before the first menstruation. Four weeks after weaning menstruation had returned in 79% and by 8 weeks after in 93% of the mothers. At 6 months postpartum, frequency of breast-feeding, and of night-time feeding were determinants of amenorrhoea.